Hydrocracking of hydrocarbon feedstocks is often used to convert lower value hydrocarbon fractions into higher value products, such as conversion of vacuum gas oil (VGO) feedstocks to diesel fuel and lubricants. One type of common reaction scheme is to use hydrocracking and dewaxing to convert a VGO feedstock into at least one lubricant basestock. A hydrocracking process can be used to convert the feed to lower boiling point molecules, saturate olefins, saturate aromatics, and/or open aromatic rings. This type of conversion process typically also results in an increase in viscosity index (VI) for the feed before it is dewaxed. The hydrocracking process can further remove contaminants from the feed, such as sulfur and nitrogen. The resulting hydrocracked and dewaxed product can be fractionated into multiple basestocks using a fractionator.
U.S. Pat. No. 4,011,154 describes a method for processing a feed to produce multiple basestocks, where the viscosity index spread of the basestocks is less than a desired value. In an example, a feedstock is fractionated into a portion boiling below about 1000° F. (538° C.) and a fraction boiling above about 1000° F. (538° C.). The lower boiling fraction is hydrocracked in a first hydrocracking zone in a reactor. The effluent from the first hydrocracking zone is combined with the heavier boiling fraction and hydrocracked in a second hydrocracking zone in the reactor. The resulting liquid product is then fractionated to form a 150N basestock, a 350N basestock, and a 1800N bright stock.
U.S. Pat. No. 6,884,339 describes a method for processing a feed to produce a lubricant base oil and optionally distillate products. A feed is hydrotreated and then hydrocracked without intermediate separation. An example of the catalyst for hydrocracking can be a supported Y or beta zeolite. The catalyst also includes a hydro-dehydrogenating metal, such as a combination of Ni and Mo. The hydrotreated, hydrocracked effluent is then atmospherically distilled. The portion boiling above 340° C. is catalytically dewaxed in the presence of a bound molecular sieve that includes a hydro-dehydrogenating element. The molecular sieve can be ZSM-48, EU-2, EU-11, or ZBM-30. The hydro-dehydrogenating element can be a noble Group VIII metal, such as Pt or Pd.
U.S. Pat. No. 7,300,900 describes a catalyst and a method for using the catalyst to perform conversion on a hydrocarbon feed. The catalyst includes both a Y zeolite and a zeolite selected from ZBM-30, ZSM-48, EU-2, and EU-11. Examples are provided of a two stage process, with a first stage hydrotreatment of a feed to reduce the sulfur content of the feed to 15 wppm, followed by hydroprocessing using the catalyst containing the two zeolites. An option is also described where it appears that the effluent from a hydrotreatment stage is cascaded without separation to the dual-zeolite catalyst, but no example is provided of the sulfur level of the initial feed for such a process.